This invention relates to an improved apparatus for pressure molding a shaped article such as a hamburger patty from a tissue containing food material such as ground raw beef that is subject to shrinkage during cooking. The apparatus provides a supply of the material, a receiver chamber such as a cylinder, a piston in the receiver chamber that is positioned away from the mold plate to provide space for a preselected amount of the material between the piston and the mold plate opening, mold filling means for forcibly moving the piston to apply pressure to the material in the receiver chamber thereby filling the mold opening, the piston having a pressure applying end that is substantially flush with the mold plate at the completion of the filling, means for thereafter moving the mold and thereby the mold opening to a position where the mold opening is out of communication with the cylinder and where the article is ejected from the mold opening and means for maintaining the piston substantially flush with the mold during this moving thereby maintaining the molding pressure on the material in the mold opening. The result is a meat-to-meat shear between the material in the mold opening and meat in the cylinder is avoided thereby preventing parallel alignment of the tissues and resulting nonuniform shrinkage. Because the apparatus of this invention avoids this parallel alignment of the tissues the articles such as a food patty maintains its uniform shape during shrinkage caused by cooking.
The most pertinent prior art of which applicant is aware is R. G. Hall U.S. Pat. No. 3,347,176 which also discloses a supply means, a cylinder and piston, a passage leading from the supply means to the cylinder and means for forcing the material from the cylinder into a mold plate opening by moving the piston toward the opening. However, the present invention has structure and advantages that are different from anything disclosed in this Hall patent as defined in the claims hereof.